The present invention relates to coupling devices of the type used to transmit torque, for example, in a vehicle drive line, and more particularly, to a coupling device of the type having a bevel gear ring gear associated therewith as the input to the coupling device. The present invention also relates even more particularly to an improved method of assembly of such a coupling device.
As used herein, the term “coupling device” will be understood to mean and include a device which is able to transmit torque from an input to one or more outputs, and in which there is a clutch assembly disposed between the input and the output, such that the torque transmission of the coupling device is in some way related to the extent of engagement of the clutch assembly. Within the scope of the present invention, the term “coupling device” means and includes both gear-type devices (such as bevel gear differentials), as well as gearless-type (clutch only) coupling devices.
Although the improved method of assembly of a coupling device may be utilized with many different types and configurations of coupling devices, such as coupling devices made in accordance with the teachings of U.S. Pat. No. 5,964,126, assigned to the assignee of the present invention and incorporated herein by reference, it is also quite advantageous when utilized in conjunction with vehicle differentials of the type illustrated and described in U.S. Pat. No. 5,310,388, also assigned to the assignee of the present invention and incorporated herein by reference. It is believed that those skilled in the art of differential and coupling devices will have a much better understanding of the potential scope of the present invention from a reading and understanding of the remainder of the specification.
A common factor in most differentials and coupling devices, of the type to which the present invention relates, is the presence of some sort of annular input ring gear (typically, of a “bevel” gear configuration) which serves as the “input” to the coupling device, in terms of the torque flow path. Typically, input drive is transmitted from the vehicle driveline by means of an input pinion gear to the ring gear, in a manner well know in the driveline art. Also typically, the housing of the coupling device defines a radially extending flange portion, and the annular ring gear is disposed about the housing of the coupling device and is fastened to the flange portion, typically by means of a plurality of bolts. The coupling device is normally manufactured by someone such as the assignee of the present invention, and is then shipped to the axle or vehicle assembly plant where the coupling device and the ring gear are fastened together, and then the entire coupling device-ring gear subassembly is installed within an outer differential housing. As is well known to those skilled in the art, it is typically the outer differential housing which serves as a fluid reservoir (low pressure source) for the lubrication fluid required for use in the coupling device. In the coupling devices of the cited patents, there is included a clutch pack operable to transmit torque between the input (the combination of the ring gear and the coupling housing) and the output (one of the axle shafts). The degree of engagement of the clutch pack is determined by fluid pressure in a piston chamber in which the fluid pressure biases a clutch piston against the clutch pack. The differential coupling devices of the cited patents include a gerotor pump, integral with the coupling device, the gerotor pump having one rotor fixed to rotate with the input and the other rotor fixed to rotate with the output. As used herein, the term “clutch pack” will be understood to mean and include not only a multiple friction disk-type clutch pack, but also, any of the other well known types of clutch assemblies, such as cone clutches, etc. in which the degree of engagement is generally proportional to the fluid pressure acting on the clutch piston, or on an equivalent clutch-engagement structure.
It should be understood that the present invention is not limited to a coupling device of the type that includes a gerotor pump, nor to a coupling device having any particular type of clutch and clutch piston arrangement, except to the extent specifically noted hereinafter in the appended claims. However, as will be understood by those skilled in the art from a reading and understanding of the subsequent specification, the assembly method of the present invention is more likely to be of benefit, and be needed, in conjunction with a coupling device having some sort of “on-board” source of fluid pressure (such as a gerotor pump) which serves as the source for pressurized fluid in the clutch piston chamber. Furthermore, the assembly method of the present invention is especially advantageous if the coupling device includes some sort of pressure control valve assembly for controlling the instantaneous fluid pressure in the piston chamber, in response to the need for torque transmission through the coupling.
In the differential coupling device of the present invention there is disposed about one end of the coupling housing a plenum member which serves, in part, to define a substantial portion of the hydraulic circuit which controls the piston apply pressure in the piston chamber. In the subject embodiment of the invention, this plenum member defines a number of required “features” as that term will be amplified and described in greater detail subsequently, one example of such a “feature” being a portion which extends radially downward into the low pressure reservoir, or sump, defined within the outer differential housing and which therefore serves as the “inlet” to the hydraulic circuit. Another example of such a “feature” is a portion which extends radially outward from the plenum member, and on which the pressure control valve assembly is mounted.
In developing a commercial embodiment of the present invention, it was determined that, partially because of such required “features” on the plenum member, the assembly process was greatly complicated and, as a result, made unacceptably expensive. It is well known to those skilled in the art of assembling such differential coupling devices, that the preferred method of assembling the coupling device and the ring gear in the axle or vehicle assembly plant is to manually insert each of the fasteners through the flange portion of the housing and partially thread the fasteners into the ring gear. Subsequently, the assembly operator would use a bolt driver, having a separate driver for each of the fasteners, such that all of the fasteners are fully threaded into the ring gear simultaneously. However, on the coupling device of the present invention, the ring gear is installed from one end of the coupling housing, until it is seated in a face-to-face relationship with the flange portion. The plenum member is disposed at the opposite axial end of the coupling housing, and therefore, the fasteners must be inserted through the flange portion and into the ring gear from the end of the coupling housing where the plenum member is disposed, and in addition, the bolt driver must be able to engage each of the bolts from the end where the plenum member is disposed.